The combustors in gas turbine engines often exhibit trade-offs between ignition and low-power operability and high-power emissions and durability. Aerodynamic flow patterns within the combustor determine, to a large extent, how the combustor performs over the full operating range of the combustor. However, it is often found that the aerodynamics associated with good ignition and low-power operability can produce increased exhaust emissions and/or high metal temperatures at high-power. Similarly, the aerodynamics associated with improved emissions and reduced metal temperatures often do not perform well during ignition and sub-idle operation.
As is generally known, many gas turbine engine combustors include swirlers. These swirlers, to a large extent impact, primary zone aerodynamics with the combustor. Thus, the ability to modulate or mode-switch between two differently configured swirlers, each optimized for either high-power or low-power (e.g., sub-idle) operation, would be of tremendous benefit in developing gas turbine combustors with substantial improvements in emissions and durability while meeting the demanding requirements for aircraft engine operability.
Moreover, it is advantageous during ignition to direct some of the fuel toward the igniter region in order to initiate the ignition process. At high-power, however, directing the fuel spray toward the igniter region may have an adverse impact on igniter durability by producing locally hot regions. It would thus be desirable to direct a portion of the fuel toward the spark region during start-up and then shift this fuel away from the igniter after ignition has occurred and high-power operation has been established, thereby reducing the local metal temperatures in this region and improving the overall durability of the igniter hardware.
Hence, there is a need for a system and method that can modulate or mode-switch between two differently configured swirlers, each optimized for either high-power or low-power (e.g., sub-idle) operation, and/or that can direct a portion of the fuel toward the spark region during start-up and then shift this fuel away from the igniter after ignition has occurred and high-power operation has been established. The present invention addresses at least these needs.